This invention relates to lighting and power systems and more particularly to an improved relocatable system in which power distribution to lighting fixtures and to a building floor area is easily modified to meet changing requirements.
Fluorescent lighting fixtures are generally used for illuminating floor areas in commercial buildings due to their efficiency as compared to other light sources, although other types of light sources such as incandescent lamps or high intensity discharge (HID) lamps or a combination of different types of lighting sources may be used. In modern construction of commercial buildings such as store and office buildings, ceiling structures generally comprise suspended ceilings which include a suspended grid system which supports ceiling panels such as fiberglass tiles. The plenum space above the suspended ceiling is used for distribution of conditioned air and electrical power to the area below the ceiling. Where the area consists of a large open area such as in a large retail store, lighting fixtures may be suspended from the grid structure which supports the ceiling tiles. However, lighting fixtures of this type are not economical or pleasing in appearance where the floor space is to be divided into a number of offices or where the ceiling is relatively low. In such cases, lighting fixtures are typically recessed into the suspended ceiling such that a lighting diffuser on each fixture extends substantially coplanar with the ceiling. In many cases, the suspended ceiling is installed prior to partitioning a floor area into individual office spaces. The use of recessed fluroescent lighting fixtures for lighting the floor area facilitates partitioning the floor area into office spaces either without moving or with a minimum moving of the lighting fixtures which are recessed into the ceiling. After the floor area is partitioned into individual offices or rooms, the lighting fixtures often must be rewired to permit switching the fixtures in each room independent of the fixtures in the remaining rooms. The rewiring of lighting fixtures adds considerably to the expense of installing the lighting system in the building. This expense is normally borne by the lighting contractor who must bid competitively for a contract to install and modify the lighting system. However, the contractor must place his bid without knowing his actual modification expense since at the time the bid is placed, the contractor may have no information on the final floor plan for the building for which he is placing the bid.
In my prior U.S. Pat. No. 3,719,768 which issued on Mar. 6, 1973, a system is disclosed which facilitates rewiring lighting fixtures after room partitions are installed. In the system disclosed in this patent, flexible electrical cords are used for connecting electrical switches and outlets mounted in wall panels with power distribution boxes and control relays located above a suspended ceiling. The power distribution boxes and relays are also connected to lighting fixtures. This system has the advantage of providing prewired wall panels which may be readily installed for partitioning a floor area into office spaces. However, the physical wiring above the suspended ceiling must be modified when the wall panels are installed in order to interconnect all lighting fixtures over a partitioned office with a wall switch. Considerable labor and expense may be required for modifying the wiring when the wall partitions are installed.
Another prior art system is shown in U.S. Pat. No. 3,683,101 which issued to Aug. 8, 1972 to Milton Liberman. In the Liberman system, prewired lighting fixtures are plugged into prewired receptacles on channels which are integral with some of the inverted T-support or grid members for a suspended ceiling. Installation of a system of this type requires less labor over systems which are entirely hand wired on the site. However, connections to the wiring in the channels must be changed when switching requirements change, as when a space below the suspended ceiling is partitioned or a partition is relocated. Furthermore, the prewired channels do not readily adapted to the switching of power to some fixtures plugged into a channel while leaving unswitched other similar fixtures plugged into the same channel, unless separate wires are run to each channel receptacle. Finally, since the channels generally are installed before the final floor plan is known, a number of the channels may ultimately be unused. This results in an increase in the installation expense for a system of this type.
Still another system is shown in the U.S. Pat. No. 4,001,571 which issued Jan. 4, 1977 to Myron D. Martin. This patent discloses a lighting system in which groups of lighting fixtures are arranged in branch circuits. A separate branch circuit cable extends between each two adjacent fixtures in the branch circuit. Electrical connections from the branch circuit cable to the lighting fixture and between two interconnected branch circuit cables are modified by inserting adapters between either the cables and the fixture or between two successive cables in the branch circuit. Adapters are also used for switching one or more of the fixtures in the branch circuit. However, this system is not readily adaptable for applications other than lighting.